During operation of a variable geometry or variable nozzle turbine (VNT), a pressure differential can be generated between a command side and a vane body side of a variable geometry mechanism. Such a pressure differential can act on various vane components and force a vane component against another component, increase force between a vane and another component and/or increase force between vane components. Consequently, an increase in pressure differential can affect vane controllability. For example, a pressure differential can force a vane post against an opposing vane side surface (e.g., turbine casing wall) and thereby increase friction and force required to initiate vane rotation and/or increase friction and force required during vane rotation. Recent trends in turbocharger technology, including higher turbine inlet pressure, higher expansion ratio of vanes and larger vane axis diameters (e.g., higher loading, potentially larger contact areas and therefore possibly more resistance), will tend to exacerbate such problems. Therefore, a need exists for technology that addresses friction problems associated with variable geometry turbines. As discussed herein, a treatment is applied to a surface that at least partially bounds or defines a space for a vane or plurality of vanes. The treatment acts to reduce friction, which can enhance controllability of a variable geometry turbine and promote longevity.